This invention relates to a method of calibrating a component, such as a sintered body which has two opposite large surfaces and a circumferential (peripheral) surface which connects the large surfaces with one another. In the circumferential surface which may have a continuous and/or polygonal contour, at least one recess is provided by undercutting.
The purpose of a calibrating process with which the invention is concerned is to complete shaped metal components made in large numbers, without expensive chip removal processes or at least by minimizing such steps. Methods used for such a purpose are pressing, pressure casting, fine casting and powder-metallurgical sintering processes performed at ambient or elevated temperatures.
In manufacturing articles by processes in powder metallurgy, powder is pressed by die punches (which may be profiled) into a suitably configured die to assume the desired shape of the component. In some instances mandrels may be used and the process is performed at elevated temperatures, if required. Thereafter the component is sintered. In such manufacturing methods the formation of undercuts at and in the component involves difficulties and therefore often a combination of a powder-metallurgical process with shaping by material removal (chip removal) is resorted to.
Such a process combination is utilized in the manufacture of disk-shaped or cylindrical sintered components, particularly shock absorber pistons. It has been heretofore conventional to provide in the shock absorber piston--formed of a single part, or a plurality of identical or unlike joined parts--a circumferential annular groove by material removal. In case the annular groove is pre-formed during the pressing of a blank parison, after sintering the groove has to be brought to the desired final dimensions by a subsequent material removing process which is time consuming and expensive.